[miles]

> On a several occasions (most recently today), Thunderbird has "lost" my mail messages that are in my inbox when I move them to a local folder. Effectively it corrupts the messages - they appear in the local folder as 1 KB messages with no subject or sender info. They are empty messages.

Apple's Mail app has had a virtually identical bug since Catalina; Michael Tsai's article on the issue currently has 636 comments:

https://mjtsai.com/blog/2019/10/11/mail-data-loss-in-macos-1...

After witnessing the bug myself, migrated to Thunderbird with Maildir enabled[1] for long-term storage; have yet to experience the issue despite a large database (>300,000 emails) and daily IMAP import to local folders.

[1] https://tinyapps.org/blog/202207100700_thunderbird_mbox_to_m...